Tech Trained Monkey

Everyday Problem Solvers

Category Archives: Troubleshooting

Analysing success

As the 1940’s air war in Europe intensified, the Allies faced a major problem. Their bombers would leave England by the hundreds, but too many of them didn’t return, brought down by extremely heavy enemy flak. The Allies desperately needed to beef up the armor on their planes to provide protection, but armoring an entire plane, or even an entire cockpit, involved far too much weight. How could they choose the few especially vulnerable places to be armored?

A couple of clever engineers solved this problem with a counter-intuitive analysis. After comprehensively logging the locations of flak damage inflicted around the fuselages, engines, and cockpits of planes returning from hundreds of bombing runs, they calculated Read more of this post


Advanced Troubleshooting Sql Server Pt.1

Detecting a Bad SPN

Okay, we all know the error that this causes. Even saying SSPI context is bad juju, and I feel dirty when I talk about it, but it has to be said:

Cannot generate SSPI Context

This is a generic error that can be caused by 1000 different things, but experience has shown me that 98% of the time, it is caused by 1 of 2 problems. Either the server is not able to connect to a domain controller to establish the SSPI context or there is an invalid SPN for the SQL Server service in AD. To verify if the domain controller connection may be a problem, I check the System event log. There may be errors stating that SQL Server was not able to connect to a domain controller or kerberos errors. The error logged may have occurred several days before you see the SSPI context errors. 99% of the time, this error is resolved by rebooting the server.

I want to talk about the second cause. An invalid SPN will cause this error. No SPN at all will NOT cause this error. That bears repeating: No SPN at all will NOT cause this error. Adding an SPN to AD will NOT fix this error. Setting up kerberos or constrained delegation when there is an invalid SPN will NOT fix this error. Starting to see a pattern? Read more of this post